Op Amp Calculations
in [Design]
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From: Jim Thompson on 5 Oct 2005 12:49 On 5 Oct 2005 09:18:39 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >Jim Thompson wrote... >> >> ... Sheeesh! ... > > Hey, that's my word! Will you share? It's a GOOD word! ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: RST Engineering (jw) on 5 Oct 2005 14:01 Jeez, all I asked as the OP was what time it was, I didn't need to know how to make the watch or the theory of molecular resonance. I'll ask a HARD question next time. {;-) Jim
From: Terry Given on 6 Oct 2005 00:45 Jim Thompson wrote: > On Wed, 05 Oct 2005 13:03:55 GMT, Fred Bloggs <nospam(a)nospam.com> > wrote: > > >> >>Fred Bartoli wrote: >> >>>"Terry Given" <my_name(a)ieee.org> a ?crit dans le message de >>>news:1128463369.256572(a)ftpsrv1... >>> >>> >>>>Fred Bloggs wrote: >>>> >>>> >>>>>Terry Given wrote: > > [snip] > >>>>>>What about the typo? the 2nd transistor shorts out the +5V supply.... >>>>>> > > [snip] > >>>>shouldnt there be something to limit current though? +5V...Vce...Vbe >>>>with nary a resistor in sight. ultimately the base current could be as >>>>high as the opamp output current (assuming negligible contribution from >>>>the summing junction).... >>>> >>>>nice artwork BTW >>>> >>> >>> >>>That, (which can be corrected by moving Q2's collector) plus Q1/Q2 operate >>>at vanishingly low IC so that the input impedance has nothing to do with >>>that of a CFB, even at moderate audio frequencies. >>> >>>Take IC3=1mA, HFE=100 for all the Qs. That makes IC1=25nA and gmQ1=1uA/V and >>>a total transconductance one third of it or gm = 0.33uA/V. >> >>Not quite, essentially all the incremental base drive voltage is >>developed across hie of the first transistor. Your reasoning is wrong >>and your estimate is high. > > > And it STILL will go up in flames during power-up. Sheeesh! Such > DESIGN ;-) > > [snip] > > ...Jim Thompson Hi Jim, can you please elaborate on why? I presume because of the 2nd transistor.... Cheers Terry
From: John Woodgate on 6 Oct 2005 03:30 I read in sci.electronics.design that Jim Thompson <thegreatone(a)example.com> wrote (in <m018k15qtpcalihfo0th9o24oqnfbpk2td(a)4ax.com>) about 'Op Amp Calculations', on Wed, 5 Oct 2005: >On 5 Oct 2005 09:18:39 -0700, Winfield Hill ><Winfield_member(a)newsguy.com> wrote: > >>Jim Thompson wrote... >>> >>> ... Sheeesh! ... >> >> Hey, that's my word! > >Will you share? It's a GOOD word! > > Offer him a half-share in 'Snooooort!' -- Regards, John Woodgate, OOO - Own Opinions Only. If everything has been designed, a god designed evolution by natural selection. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
From: Winfield Hill on 6 Oct 2005 04:12
John Woodgate wrote... > Jim Thompson wrote ... >> Winfield Hill wrote: >>> Jim Thompson wrote... >>>> >>>> ... Sheeesh! ... >>> >>> Hey, that's my word! >> >> Will you share? It's a GOOD word! > > Offer him a half-share in 'Snooooort!' Plus a half share of Bwaahahahaha! -- Thanks, - Win |